Electrical connectors – Electromagnetic or electrostatic shield – Shielding individually surrounding or interposed between...
Reexamination Certificate
1999-05-25
2001-08-21
Vu, Hien (Department: 2833)
Electrical connectors
Electromagnetic or electrostatic shield
Shielding individually surrounding or interposed between...
C439S108000
Reexamination Certificate
active
06276965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates generally to electrical connectors. More particularly, embodiments of the present invention relate to an improved electrical connector that is electromagnetically shielded and provides for a secure, low-profile physical/electrical connection with a mating media plug.
2. The Relevant Technology
The demand for personal computers and related equipment continues to expand due to a number of factors. One important factor is in that the prices of computers continues to decline. Another factor is the expansion and development of the Internet and related network communications. More and more commercial and non-commercial enterprises are conducting business via the Internet and consumers need personal computers to gain access to the products and information that are available on the Internet.
In addition to being more affordable, advances in computer application software, operating systems and communications software has fueled the development of computers having greater processing speeds and capacities. At the same time, the pressure to at least maintain, or preferably reduce, the physical size of the computer has increased as well. Accordingly, downsizing and miniaturization of computer components is an issue of great importance in the industry.
In an effort to reduce the form factor of the typical personal computer, and yet expand the capabilities of that computer, manufacturers began to develop miniature portable expansion devices having smaller sizes, such as add-on memory cards and modems. The typical expansion device was designed to plug into a port or socket on the main computer; thus the expansion device served to expand the capability of the computer without significantly increasing the size of the computer's physical envelope.
While the development of portable expansion devices represented a significant advance in the capabilities of personal computers, one drawback of many of the devices was that they were designed to fit only one manufacturer's computer, and thus were not interchangeable between platforms. The industry recognized that standardization of these devices would, among other things, greatly increase the demand for them. To this end, several manufacturers collaborated to form the Personal Computer Memory Card International Association (PCMCIA). This body developed and promulgated standards for the physical design, dimensions, and electrical interface of expansion devices. Now, many computers being manufactured, especially those having a reduced size, are adapted to accommodate these standards.
PCMCIA cards have become very popular because of their relatively small size, interchangeability, and capability. However, as a result of the relentless drive for smaller and more capable computers, the industry has developed a new generation of expansion devices with an even smaller form factor than that of PCMCIA cards. The new expansion devices, or cards, are sometimes referred to as “compact flash” or “miniature flash” cards.
Some examples of the new devices include compact flash memory cards, which are solid state storage devices that may have a storage capacity as high as 40MB; modems; and local area network (LAN) cards. The new compact devices have a very small “form factor” or physical size. A typical compact flash card uses about 1550 mm
2
(36 mm long×43 mm wide) of space on a circuit board. In contrast, a typical card built to PCMCIA standards uses almost three times as much circuit board space, or about 4644 mm
2
(86 mm long×54 mm wide).
Clearly, the compact flash form factor represents an important advancement in the art. However, the smaller form factor has also created some new problems that must be overcome in order that the maximum performance and reliability of the compact flash cards may be realized. Certain of these problems are particularly acute in those compact flash LAN cards that use a 4 pin input/output (I/O) connector. Some of the problems flowing from the use of the new form factor concern the construction and composition of the compact flash media card. Other problems concern the physical and electrical interfaces between the compact flash card and the various types of media cables used to carry media between the flash card and other devices.
One of the shortcomings common in current compact flash card designs concerns the harmful electromagnetic radiation produced by the card. Electromagnetic radiation is a natural consequence of current flow through the electrical circuits on the card. Unchecked, electromagnetic radiation can interfere with and disrupt the operation of electrical and electronic circuits in the host device. The interference resulting from electromagnetic radiation is commonly known as electromagnetic interference (EMI). Because electromagnetic radiation is a natural consequence of current flow, it cannot practically be prevented. Instead, emissions of the electromagnetic radiation must be controlled in order to prevent harmful EMI from resulting.
It is generally acknowledged that metal or metallic structures, if properly located and grounded, can be effective in controlling harmful electromagnetic radiation. Metals are effective in this regard because they generally have a low characteristic impedance which has the desirable characteristic of reflecting the high impedance electromagnetic radiation typically emitted by computers and related devices. By reflecting the electromagnetic radiation away from vulnerable circuits or devices, the metal thereby acts as a protective shield. Materials which can absorb electromagnetic radiation would be effective as well. However, typical compact flash cards are housed in a bay or enclosure, inside the host device, that is constructed of plastic or the like. The non-metallic enclosures are largely ineffectual in reflecting the electromagnetic radiation produced by the card. Furthermore, even though many compact flash cards employ metal covers, those covers are nevertheless inadequate to reflect electromagnetic radiation. This is due to the fact that effective EMI control cannot be achieved unless the metal covers typically utilized in compact flash cards are electrically bonded together and grounded. Since the metal covers of typical compact flash cards are not bonded and grounded, those covers are generally of little use in preventing PCB-generated EMI.
While it is clear that there are unresolved concerns regarding EMI and the construction of the compact flash cards, EMI problems are not limited solely to the card itself. As suggested earlier, some of the problems flowing from the new compact flash form factor relate to the physical/electrical interface used to connect a media cable to the card.
In particular, the current flowing through the media cable and the physical/electrical interface, or I/O connector, generates electromagnetic radiation which, in turn, causes harmful EMI. Many of the connectors currently in use with the compact flash card, including the 4 pin connectors, lack any device or means to reflect or absorb the electromagnetic radiation produced by the connector. Thus, when a media plug at the end of the media cable is inserted into the compact flash card connector, the unchecked electromagnetic radiation that is produced as a result of current flow through the connector, acts to interfere with the operation of electrical and electronic components inside the compact flash card and in the host device.
Not only are the typical compact flash card I/O connector designs ineffectual in preventing harmful EMI, those connectors suffer from other shortcomings as well. A significant problem concerns the structural configuration of the typical connector. In particular, the physical shape of the receiving portion, or aperture, of the connector, i.e., the portion that receives a mating media plug, is such that the connector can readily accommodate modular plugs. For instance, the connector may be capable of receiving a modular plug from a telephone line or a network line. This
Hien TG
Madsen Brent D.
Wong Margaret
3Com Corporation
Vu Hien
Workman, Nydegger & Seely
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